A perchlorate, as described in detail in Non-Patent Document 1 or 2 below, is manufactured industrially by electrolytically oxidizing an aqueous solution of sodium chlorate that has been synthesized by electrolytically oxidizing an aqueous solution of sodium chloride and then performing a predetermined treatment. Here, examples of an electrolysis cell (an electrolysis tank) used for electrolytically oxidizing the aqueous solution of sodium chloride include a diaphragm-free cell described in Patent Document 4 below, in which no diaphragm is provided between electrodes, and an electrolysis cell described in Patent Document 1 or 2 below, in which a diaphragm is provided between electrodes.
Here, a method of industrially manufacturing a perchlorate will be described using ammonium perchlorate as an example. A conventional method of industrially manufacturing ammonium perchlorate consists of, roughly, the following two processes.
(1) Electrolytic oxidation of sodium perchlorate (NaClO4)
(2) Metathetical reaction of sodium perchlorate and ammonium sulfate ((NH4)2SO4)
In the process (1), an aqueous solution of sodium chlorate (NaClO3) is electrolyzed without using a diaphragm so as to oxidize sodium chlorate and thus obtain sodium perchlorate. The entire reaction in the process (1) is expressed by the following chemical equation (a).NaClO3+H2O→NaClO4+H2  (a)
Here, for example, a piece of titanium having platinum coated on the surfaces is used as the anode, and, for example, iron is used as the cathode.
In the process (2), ammonium sulfate ((NH4)2SO4) is added to the aqueous solution of sodium perchlorate, and ammonium perchlorate (NH4ClO4) is obtained by a metathetical reaction. The entire reaction in the process (2) is expressed by the following chemical equation (b).2NaClO4+(NH4)2SO4→2NH4ClO4+Na2SO4  (b)
Meanwhile, when ammonium perchlorate is used as an oxidizing agent of a propellant, there are cases in which the ammonium perchlorate needs to be, for example, fine crystals having a grain size of about 1 μm to 10 μm as described in Patent Document 3 below. Here, examples of a method of obtaining the fine crystals include a salting out method described in Non-Patent Document 3 or a method described in Patent Document 5, in which ammonia gas and the vapor of an anhydrous perchlorate are mixed so as to crystallize the ammonia perchlorate.
In addition, as another example of the method of industrially manufacturing a perchlorate, a method of manufacturing lithium perchlorate will be described. The method of industrially manufacturing lithium perchlorate consists of the following four processes including a process in which lithium perchlorate is manufactured from sodium chlorate.
(I) Manufacture of sodium perchlorate (NaClO4)
(II) Manufacture of potassium perchlorate (KClO4)
(III) Manufacture of perchloric acid (HClO4)
(IV) Manufacture of lithium perchlorate (LiClO4)
In the process (I), an aqueous solution of sodium chlorate (NaClO3) is electrolyzed without using a diaphragm so as to oxidize sodium chlorate and thus obtain sodium perchlorate. The entire reaction in the process (I) is expressed by the following chemical equation (A).NaClO3+H2O→NaClO4+H2  (A)
In the process (II), potassium chloride (KCl) is added to the aqueous solution of sodium perchlorate, and potassium perchlorate is obtained by a metathetical reaction. The entire reaction in the process (II) is expressed by the following chemical equation (B).NaClO4+KCl→KClO4+NaCl  (B)
Meanwhile, it is also possible to generate potassium perchlorate through the self-oxidation of potassium chlorate (as shown in the following chemical equation (C)), but the yield is low with respect to a raw material, and therefore this method is not suitable for mass production.4KClO3→3KClO4+KCl  (C)
In the process (III), the aqueous solution of potassium perchlorate is heated and decomposed using concentrated sulfuric acid (H2SO4). The entire reaction in the process (III) is expressed by the following chemical equation (D).KClO4+H2SO4→KHSO4+HClO4  (D)
When the solution obtained in the above process is distilled in vacuum, an anhydrous perchlorate is crystallized.
In the process (IV), lithium carbonate (Li2CO3) is added to an aqueous solution of perchloric acid, and lithium perchlorate is synthesized through a neutralization reaction. In addition, the aqueous solution of lithium perchlorate synthesized by the neutralization reaction is evaporated and crystallized so as to obtain lithium perchlorate trihydrate. The neutralization reaction in the process (IV) is expressed by the following chemical equation (E).2HClO4+Li2CO3→2LiClO4+CO2+H2O  (D)